cmnt: [SRU][Bionic][PATCH 2/2] rtc: opal: Fix OPAL RTC driver OPAL_BUSY loops

Khaled Elmously khalid.elmously at canonical.com
Mon Jun 18 18:41:54 UTC 2018


On 2018-06-13 11:10:08 , Joseph Salisbury wrote:
> From: Nicholas Piggin <npiggin at gmail.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1773964
> 
> The OPAL RTC driver does not sleep in case it gets OPAL_BUSY or
> OPAL_BUSY_EVENT from firmware, which causes large scheduling
> latencies, up to 50 seconds have been observed here when RTC stops
> responding (BMC reboot can do it).
> 
> Fix this by converting it to the standard form OPAL_BUSY loop that
> sleeps.
> 
> Fixes: 628daa8d5abf ("powerpc/powernv: Add RTC and NVRAM support plus RTAS fallbacks")
> Cc: stable at vger.kernel.org # v3.2+
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> Acked-by: Alexandre Belloni <alexandre.belloni at bootlin.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> (cherry picked from commit 682e6b4da5cbe8e9a53f979a58c2a9d7dc997175)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> ---
>  arch/powerpc/platforms/powernv/opal-rtc.c |  8 ++++---
>  drivers/rtc/rtc-opal.c                    | 37 +++++++++++++++++++------------
>  2 files changed, 28 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/opal-rtc.c b/arch/powerpc/platforms/powernv/opal-rtc.c
> index f886886..aa2a513 100644
> --- a/arch/powerpc/platforms/powernv/opal-rtc.c
> +++ b/arch/powerpc/platforms/powernv/opal-rtc.c
> @@ -48,10 +48,12 @@ unsigned long __init opal_get_boot_time(void)
>  
>  	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
>  		rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
> -		if (rc == OPAL_BUSY_EVENT)
> +		if (rc == OPAL_BUSY_EVENT) {
> +			mdelay(OPAL_BUSY_DELAY_MS);
>  			opal_poll_events(NULL);
> -		else if (rc == OPAL_BUSY)
> -			mdelay(10);
> +		} else if (rc == OPAL_BUSY) {
> +			mdelay(OPAL_BUSY_DELAY_MS);
> +		}
>  	}
>  	if (rc != OPAL_SUCCESS)
>  		return 0;
> diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c
> index 304e891..60f2250 100644
> --- a/drivers/rtc/rtc-opal.c
> +++ b/drivers/rtc/rtc-opal.c
> @@ -57,7 +57,7 @@ static void tm_to_opal(struct rtc_time *tm, u32 *y_m_d, u64 *h_m_s_ms)
>  
>  static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
>  {
> -	long rc = OPAL_BUSY;
> +	s64 rc = OPAL_BUSY;
>  	int retries = 10;
>  	u32 y_m_d;
>  	u64 h_m_s_ms;
> @@ -66,13 +66,17 @@ static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
>  
>  	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
>  		rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
> -		if (rc == OPAL_BUSY_EVENT)
> +		if (rc == OPAL_BUSY_EVENT) {
> +			msleep(OPAL_BUSY_DELAY_MS);
>  			opal_poll_events(NULL);
> -		else if (retries-- && (rc == OPAL_HARDWARE
> -				       || rc == OPAL_INTERNAL_ERROR))
> -			msleep(10);
> -		else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)
> -			break;
> +		} else if (rc == OPAL_BUSY) {
> +			msleep(OPAL_BUSY_DELAY_MS);
> +		} else if (rc == OPAL_HARDWARE || rc == OPAL_INTERNAL_ERROR) {
> +			if (retries--) {
> +				msleep(10); /* Wait 10ms before retry */

I was expecting this msleep() to use the new OPAL_BUSY_DELAY_MS instead of a hardcoded 10 .. wasn't that the whole point?

> +				rc = OPAL_BUSY; /* go around again */
> +			}
> +		}
>  	}
>  
>  	if (rc != OPAL_SUCCESS)
> @@ -87,21 +91,26 @@ static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)
>  
>  static int opal_set_rtc_time(struct device *dev, struct rtc_time *tm)
>  {
> -	long rc = OPAL_BUSY;
> +	s64 rc = OPAL_BUSY;
>  	int retries = 10;
>  	u32 y_m_d = 0;
>  	u64 h_m_s_ms = 0;
>  
>  	tm_to_opal(tm, &y_m_d, &h_m_s_ms);
> +
>  	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
>  		rc = opal_rtc_write(y_m_d, h_m_s_ms);
> -		if (rc == OPAL_BUSY_EVENT)
> +		if (rc == OPAL_BUSY_EVENT) {
> +			msleep(OPAL_BUSY_DELAY_MS);
>  			opal_poll_events(NULL);
> -		else if (retries-- && (rc == OPAL_HARDWARE
> -				       || rc == OPAL_INTERNAL_ERROR))
> -			msleep(10);
> -		else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)
> -			break;
> +		} else if (rc == OPAL_BUSY) {
> +			msleep(OPAL_BUSY_DELAY_MS);
> +		} else if (rc == OPAL_HARDWARE || rc == OPAL_INTERNAL_ERROR) {
> +			if (retries--) {
> +				msleep(10); /* Wait 10ms before retry */

Same as above.

> +				rc = OPAL_BUSY; /* go around again */
> +			}
> +		}
>  	}
>  
>  	return rc == OPAL_SUCCESS ? 0 : -EIO;
> -- 
> 2.7.4
> 
> 
> -- 
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